# [Gmsh] Symmetric part of a geometry modifying the msh file

**Luca Bonfiglio**
bonfi at MIT.EDU

*Mon Jan 20 19:00:19 CET 2014*

Hello,
I have an issue trying to modify an .msh file.
I wrote a code to generate the .geo file needed to mesh a 2D symmetric geometry. The.geo file generates only the y positive part of the geometry and I would like to work on the .msh file to create the y negative part.
For one half of the geometry I used to have:
number of nodes= N.
number of elements= M
I added N nodes in order to get 2N nodes, where the line for node(N+1) is:
(node(N)+1) x(1) y(1)*-1 z(1)
and elements in order to get 2M elements where the line for the element(M+1) is:
(element(M)+1) elm-type(1) tag1(1) tag2(1) tag3(1) node1(1)+N node1(1)+N […] nodek(1)+N
But I got the following error:
Info : Vertex numbering is dense
Info : 92676 elements
Error : Error loading 'complete.msh'
I attach the file for the only y positive geometry (oneHalf.geo; oneHalf.msh) and the file for the complete geometry (complete.msh)
How can I solve this problem?
This is meant to be part of my PhD thesis and I'm really stuck with that…Any help would be really really appreciated!!!!
Thank you very much
Regards
Luca
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